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Discussion Starter #1
In my quest to push my 3300 lb (with driver) street mustang into the 7s in the 1/4 mile, I decided to change up my combo a good bit for 2020:

Man O War block, 3.25 Magnum crank, Oliver billet 5.4 Rods, Diamond 4.125 Pistons
AFR 220 heads, Solid roller (252/258 @ .050 & .698/.692 114 LSA), Jesel 1.6s
Ported Victor 5.0 EFI w/75mm TB (3" charge pipe), Big fuel system on C16
Turbonetics 7668s with .81 AR EHs
Holley Dominator EFI
Rossler TH400 with 2nd gear launch brake (2.48 1st gear), PTC Converter, 8.8 w/3.27s & 28" 275 DR
Full 3" exhaust to include XR-1 Mufflers and Tail pipes

Car went 8.46 @ 162 with smaller heads, HR cam shifting at 7k with Turbonetics 6668 (.68 AR EH) at 25 psi
Wasn't a clean run...converter went south and was slipping on top end a good bit.

My goal is to make enough power with the bigger turbos and SR cam/heads to bump into the high 7s with around 20 psi boost and 7500 + rpm shift point...what are your thoughts?

Has anyone run a similar, large turbo/small cube combo with success in the past? Experiences? Any tips?

I'm going to try to tune the spool time increase out of the larger turbos if possible. I'm wondering what rpm I'll need to sit on the brake at to get the 76s to launch at around 5 or 6 psi?
 

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Got everything put together yet or still waiting for parts?


Sent from my iPhone using Tapatalk
 

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Discussion Starter #5
Got everything put together yet or still waiting for parts?


Sent from my iPhone using Tapatalk
Haven't started assembling anything yet. Just had my machine shop balance my crank, needed one piece of heavy metal, which wasn't too bad. Still haven't received my heads, cam or lifters yet. I'm in no hurry, I'm currently building a 461 stroker Pontiac for my Dad's 70 GTO, so that will keep me busy for the next month or so. Too many damn projects! LOL!
 

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Wow i have a 363 that iam building now. Was thinking about twin 7675s i have 1 already. But maybe i will sell and do 2 smaller turbos. I think you can make the power you need.will the car handle it would be my question.
 

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Chassis. Saftey, its been my experience that power is easy to make these days,using it effectively is a different story. Iam a big sbf fan i hope you run the number you want nothing like a 7 sec 8.2.
 

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Discussion Starter #9
Chassis. Saftey, its been my experience that power is easy to make these days,using it effectively is a different story. Iam a big sbf fan i hope you run the number you want nothing like a 7 sec 8.2.
Yes...safety is ALWAYS a concern for me. And, for sure, if the Chassis isn't there...well, then all the power in the world means nothing. I'll creep up on the power until it is in the 7s and, hopefully, any possible issues will surface without incident, allowing me to make corrections along the way. It's always been an adventure...I think that is a big part of the fun of this hobby. And a big thanks for your support on my goal! Good luck with your project as well...sounds like it will be a mean machine!!
 

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Haven't started assembling anything yet. Just had my machine shop balance my crank, needed one piece of heavy metal, which wasn't too bad. Still haven't received my heads, cam or lifters yet. I'm in no hurry, I'm currently building a 461 stroker Pontiac for my Dad's 70 GTO, so that will keep me busy for the next month or so. Too many damn projects! LOL!
Nice!!!! I love goats, never see many around here.. Any pics???? :)
 

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Discussion Starter #13
Not to go off track but what’s the new specs on the stroker you’re building him?
'72 400 block with billet 4-bolt main caps...original block had a cracked main web.
Eagle 4340 4.250 internal balance crank
Eagle 4340 6.800 H Beam rods with ARP 2000 bolts
DSS GSX 4.150 Forged pistons, 10.5 to 1 w/72 cc head
Butler 325 CNC Ported Edelbrock Round Port Aluminum heads: 2.17 intake/1.77 exhaust valves
Northwind CNC port match single plane intake manifold w/ 950HP carb
Lunati VooDoo HR cam: 243/251 @ .050 .560/.565 110 LSA
Doug's 2" Primary Long-Tube Ceramic Headers w/3.5" Collectors into 3" Flowmasters
4-Speed Car with 4.10 Gears...Should make enough power to put its heavy 3900 weight into the 11s, but mainly want to annoy the neighbors with loud exhaust and smoking the tires in every gear! LOL!
 

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I don't think you are gaining much by staying with the same turbine wheel. You will have to push them well into 30s for boost even to the point of possibly pushing the head gaskets.

I had those turbos and made about 1100rwhp on 25ish lbs of boost on a 427, I had too much motor for the little turbine wheels.

I would look at something with a 73mm ( borg s300s ),75mm ( precision), or 78 ( VS racing ) turbine wheel to keep back pressure down.
 

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What is the advantage of the larger turbo at the same boost? It it air quality/temperature? Why is 25 psi not the same regardless of where it came from?
 

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What is the advantage of the larger turbo at the same boost? It it air quality/temperature? Why is 25 psi not the same regardless of where it came from?
Efficiency of compressor will change post wheel outlet temps which can make it easier to cool down later

Boost is not the same as cylinder pressure. Head gasket wont fail simply because of high boost. Only if there is also high cyl pressure. 30 psi 1100 whp small turbos isnt much different than 20 psi 1100 whp from different turbo if they both same power and rpm range.

68 f-1 wheel turbine isnt bad for a 347” motor.
 

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I don't think you are gaining much by staying with the same turbine wheel. You will have to push them well into 30s for boost even to the point of possibly pushing the head gaskets.

I had those turbos and made about 1100rwhp on 25ish lbs of boost on a 427, I had too much motor for the little turbine wheels.

I would look at something with a 73mm ( borg s300s ),75mm ( precision), or 78 ( VS racing ) turbine wheel to keep back pressure down.
I agree. It sounds like you are turbine limited, not compressor. What was the thought process in moving up to a 76mm compressor and keeping the 68mm turbine? I would have went the other direction with a 6875.
 
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